Apparatus for temporary storage of articles

ABSTRACT

Apparatus for temporary storage of articles, particularly thin flat articles such as letters, the apparatus having a helical shelf rotatable about its vertical axis, and conveying means for the letters which accept the letters from a fixed delivery point and stack them as a row along the shelf, the letters being orientated in vertical planes radial to the shelf axis. The conveyor means preferably includes a feeder/stacker adjacent the shelf capable of operating either to feed letters from a stack on the shelf and to convey them to another machine, or to deliver the letters to the shelf and stack them. In the preferred embodiment, the shelf rotates about its vertical axis, without vertical movement, during the feeding or stacking operations, and the feeder/stacker moves vertically to maintain a constant relationship with the surface of the shelf.

United States Patent [191 [111 3,869,115 Barkley 5] Mar. 4, 1975 1 APPARATUS'FOR TEMPORARYSTORAGE OF ARTICLES lnventor: Ronald A. Barkley, PO. Box ll 18 Station H, Ottawa, Ontario, Canada Filed: Aug. 27, 1973 Appl. No: 391,097

Foreign Application Priority Data Aug. 29, 1972 Great Britain 4004/72 References Cited UNITED STATES PATENTS 10/1964 Welland 214/7 7/1967 Pass .1 271/145 12/1969 Rothschild 198/136 8/1971 Whitfield 198/136 Primary E.raminer-Richard A. Schacher Assistant E.\'aminer-Rich'ard K. Thomson Attorney, Agent, or FirmBrowne, Beveridge, Degrandi & Kline [5 7] ABSTRACT Apparatus for temporary storage of articles, particularly thin flat articles such as letters, the apparatus having a helical shelf rotatable about its vertical axis, and conveying means for the letters which accept the letters from a fixed delivery point and stack them as a row along the shelf, the letters being orientated in vertical planes radial to the shelf axis. The conveyor means preferably includes a feeder/stacker adjacent the shelf capable of operating either to feed letters from a stack on the shelf and to convey them to an other machine, or to deliver the letters to the shelf and stack them. In the preferred embodiment, the shelf rotates about its vertical axis, without vertical movement, during the feeding or stacking operations, and the feeder/stacker moves vertically: to maintain a constant relationship with the surface of the shelf.

21 Claims, 5 Drawing Figures APPARATUS FOR TEMPORARY STORAGE OF ARTICLES The present invention relates to apparatus for storing articles, and in particular to an apparatus providing temporary storage of thin flat articles such as letters.

In existing machinery used for mechanizing the handling or processing of letter mail, apparatus to accept the output of letters from one machine, to store the letters temporarily, and to provide the input of another machine, has been neglected. Machines are available and being used to process 8-10 letters per second but these machines are still fed from trayed letter mail, each tray containing only 600-800 letters. As a result considerable manpower is expended removing letters from trays and manually locating them on the feeder unit, then removing them from the stacker at the output of the unit and putting the letters back into trays to be transported to the next processing operation.

The present invention provides apparatus, which may be termed a buffer stacker, which can stack, store and feed letters in a semiautomatic fashion. Such an apparatus may be placed at the output of a machine and set in the stack mode to accept letters automatically and stack them in the apparatus until this is filled. The apparatus is preferably portable so that, after being filled, it may be moved to the input of another machine and switched to the feed mode to provide letters, on demand, to the machine. The apparatus may be designed to be capable of stacking and de-stacking letters at a rate of 10 letters per second or more.

Apparatus in accordance with the invention basically comprises a storage unit in the form of a helical shelf with a vertical axis and mounted for rotation around this axis, and conveying means providing for movement of articles seriatim between the shelf and a stationary delivery point outside the shelf along a path which remains substantially fixed in lateral position (i.e., in plan view) as the shelf rotates and which leads directly to different positions along the shelf depending on the rotational position of the shelf. Also, the apparatus has means for providing relative vertical movement between the storage, unit and a part of the conveyor means adjacent the shelf so as to maintain a constant relationship thereof to the surface of the shelf as the shelf rotates. I r I Preferably, the storage unit is mounted for rotation without vertical movement, the part of the conveyor means adjacent the shelf being vertically movable by an amount equivalent to the overall axial height of the shelf.

Previously, it has been known to provide devices in the form of helical conveyors which, by reason of the length of conveyor which is accommodated in a relatively small space, also serves as a temporary storage. However, in such devices, the articles are fed along a helical path, either by means of belts moving along a helical track, .or by pushers which push the articles along a stationary helical track, or by vibrating a helical conveyor. None of these devices however uses a helical shelf which is mounted for rotation around its axis, and none provides conveyor means moving the articles along a path which remains substantially fixed in lateral position as the shelf rotates, and which leads directly to different positions on the shelf.

Where the apparatus is specially designed for use with thin flat articles such as letters, the conveying means preferably include pinch belt means. Since, in the preferred arrangement, the storage unit rotates without vertical movement, the pinch belt means itself must allow for movement of that part of the conveyor means adjacent the shelf so as to maintain a constant relationship thereof with the shelf as this rotates. This movable end part of the pinch belt means is preferably so disposed as to hold the articles in a vertical plane while moving these laterally and allowing transfer of the articles between the pinch belt means and different positions on the shelf whereon the articles are stacked side by side in vertical planes radial to the shelf axis. The pinch belt means also include an intermediate part twisted through relative to the movable end part, the intermediate part providing an inclined path of varying length between a delivery end part of the pinch belt means, which remains stationary, and the movable end part.

The movable end part of the pinch belt means may include a set of pinch belts carriedby a feeder/stacker operable selectively to feed articles seriatim from a stack of the articles on the shelf into a main set of pinch belts, or to transfer the articles from the main set of pinch belts onto the shelf to form a stack of the articles in side-by side relationship.

The use of pinch belts as described necessitates that the thin flat articles be flexible. However, this does not i pose any difficulties when the apparatus is used as part of an automatic letter handling installation, since such installations are routinely provided with means for automatically rejecting letters having less than a standard degree of flexibility.

The invention also includes a process for temporarily storing fiat thin articles such as letters, as set out in the appropriate appended claims.

The invention will be more particularly described by way of example with reference to the accompanying drawing, showing a preferred embodiment, in which:

FIG. 1 shows an elevation of the apparatus,

FIG. 2 shows a further elevation partly broken away, viewed on lines 22 of FIG. 1,

FIG. 3 is a sectional plan view on line 3-3 of FIG.

I 1, and showing the feeder/stacker in the stacker mode,

FIG. 4 is a detail view on lines 4-4 of FIG. 3 showin details of the feeder/stacker, and

FIG. 5 is a further detail view of the feeder/stacker on lines 5-5 of FIG. 3.

Referring particularly to FIGS. 1 and 2, the buffer stacker has a support 10 including four vertical members 12 of square tubing connected by upper and lower horizontal frames 13, and is mounted on small wheels or castors 15 which allow the unit to be moved around to different machines with which it: is to be used. The frames 13 carry upper and lower bearings for a central vertical shaft 18,which carries a storage unit in the form of a continuous helical (or spiral) shelf 20 which is co-axial with and encircles the shaft 18. The shelf 20 is annular in plan view (FIG. 3), being horizontal in the radial direction, and is carried by rods 19 extending radially from the shaft 18. The shelf is suitable for receiving letters or like flat thin articles, stacked along the shelf side-by-side and occupying vertical planes, the upper-most articles being supported by vertical abutment 20a at the top end of the shelf. An electric motor 22 is provided for rotating the shaft 18, the arrangement being such that this motor operates in a stalled condition so that the shaft is subjected merely to light 3 rotational pressure during stacking and destacking of letters.

The buffer stacker also includes conveying means carried by support for conveying letters from a stationary delivery point A and stacking them on the shelf 20, the same conveying means being also usable to feed letters from the same stack and convey them to the delivery point.

The conveying means includes pinch belt means comprising a main pair of opposedpinch belts 30 each in the form of a closed loop having an operative reach 35 and a return reach 36, the loops each having one end held by one of two stationary vertical pulleys 32 (i.e., pulleys with vertical axes) at point A and having their other end held by one of two movable vertical pulleys 33. The pulleys 32 are driven by electric motor 34, which provides enough power to drive the whole of pinch belts.30. The pulleys 33 are adjacent the inlet end of a feeder/stacker assembly 23 to be described in detail below. The feeder/stacker and the pulleys 33 are all mounted on a carriage 24 which moves in such manner as to maintain a constant relationship with the surface of the adjacent part of shelf 20 as this rotates.

Carriage 24 includes a base plate 25 supported by a nut 26a mounted on a vertical lead screw 26 held by bearings in the upper and lower frames 13. Lead screw 26 is driven by an electric motor 27 mounted on the lower frame 13, and this motor is controlled by sensing means in the form of a tracking cam 18 mounted on base plate 25 and having an arm 28a which projects through an aperture in' the plate 25 and which contacts an area of shelf 20 underneath the plate 25, the cam being spring biased to maintain contact with the shelf. The cam operates two switches 28b and 280, switch 28b engaging the cam in such a way as to be operated whenever the height of the shelf deviates by more than a predetermined amount from the height of the carriage, and the switch 280 having poles which switch over according to the position of the cam and thus controlling the direction ofrotation of motor 27,. A control circuit connects these switches with motor 27 in such manner that when switch 28b is closed it energises a circuit through the switch 280 and thus operates motor 27 to cause the lead screw to rotate to maintain the position of carriage 24 relative the adjacent portion of shelf 20 as the shelf rotates. The carriage 24 is located in the horizontal plane by a roller 29 bearing against a vertical flat surface 29a which is the outerflange of an angle member extending between the upper and lower frames 13. The roller 29 is held pressed against this surface 29a by the tension of the pinch belts 30.

The stationary vertical pulleys 32, along with motor 34, and stationary horizontal pulleys 40, 41, and 47 to be described, are held by further, normally stationary, carriage means 100. These carriage means 100 include a vertical plate 101 carrying a bracket 102 which supports pulleys 32 and motor 34. The vertical edges of plate 101 are slidable in grooves formed between vertical angle members 103 and 104, and outer retaining strips 106. Angle member 103 is fixed to the adjacent corner member 12a, and angle member 104 is fixed to angle member 29a. The carriage means 100 includes a nut 108 engaged by vertical lead screw 109 which extends between bearings in upper and lower frames 13, and lead screw 109 is manually rotatable by hand wheel 110 to adjust the height of carriage 100 and thus the height of delivery point A. The references to this delivi cry point being stationary will thus be understood to include the case where the height of this is adjustable as described, the delivery point however normally remaining stationary during a stackingor feeding operation.

The operative reaches 35 of the pinch belts 30 move along close together at the same speed and are such as to grip individual letters between them and to convey the letters along the path between pulleys 32 and 33, this path being substantially fixed in lateral position,

i.e., in plan view. The belts are disposed in the vertical plane where they pass around the pulleys 32 and 33, but both the operative reaches and the return reaches of the belts include intermediate parts twisted through relative to the ends. The intermediate part 37 of the operative reaches of the belts provide an inclined path of variable length between a stationary delivery end part 38 of the belts (terminated by pulleys 32) and an opposite end part 39 of the belts (terminated by pulleys 33) adjacent the feeder/stacker and movable vertically therewith, and forming a portion of the movable end part of the whole pinch belt means. The junction between the intermediate part 37 and the stationary delivery end part 38 of the pinch belts is defined by a first set of horizontal pulley means including two pairs of stationary horizontal pulleys 40 and 41 level with the vertical pulley 32, the belts being twisted 90 between these horizontal and vertical pulleys. Similarly, the junction between the intermediate part 37 and the movable end part 39 of the pinch belts is defined by a second set of horizontal pulley means in the form of two pairs of pulleys 43 and 44 which are level with the vertical pulleys 33 and movable vertically therewith, being carried by vertical plate 25a of carriage 24. The operative reaches of the belts pass from pulleys 43 to pulleys 33 over a series of vertical pulleys 45a, b, c, the belts also having a 90 twist between horizontal pulleys 43, 44 and the first vertical pulley 45a. Also, the belts are bent around a total angle of about 90 (while remaining vertical) in passing over pulleys 45a, b, c, so that the operative reach of the belts adjacent pulleys 33 is perpendicular to that adjacent pulleys 32.

Since the pulleys 43, 44 (along with pulleys 33 and 45a, 1), c) are all movable in the vertical direction, without lateral movement, with the carriage 24, the length of the intermediate part 37 of the operational reaches of the belts varies. This variation is allowed for by providing extended loops 36 of the return reaches of the pinch belts, which extend between horizontal pairs of fixed and movable pulleys 47a and 47b and which are held well away from the operative reaches by further pulley means 48, these pulleys 48 being held by arms 49 biased by springs 49a away from the operational reaches of the belt to hold these reaches taut in spite of movements of the carriage.

As will be clear from FIG. 1, the pulleys 40, 41 43 and 44 are arranged in pairs above and below the operativereaches 35 of the belts. In the position shown in FIG. 1 the upper pulleys 40, 41, and lower pulleys 43, 44 are operative, but when carriage 24 has moved down below the level of A the lower pulleys 40, 41, and upper pulleys 43, 44' will be operative.

As will be seen in FIG. 3, the pulleys 33 are aligned with the discharge point of a further pair of pinch belts 50 which form another portion of the movable end part of the pinch belt means, and which also form part of the feeder/stacker, so that letters can be transferred from pinch belts 30 to shelf 20 and vise versa.

The pinch belts 50 are vertically'oriented throughout their length. They include-a narrow high friction transport belt 50a, and a complementary belt 50b which lies close against belt 50a:to provide.a,pinch belt transport path from pulleys. 57a, b (defining an inlet into this transport path.)-to pulleys 58a,' 'b which define an outlet from the path. Belt 50a has a portion which extends radially over a part of the shelf and which is located by central portions of pulleys 60 and 6-1, and this belt also passes overpulley 62 and a series of pulleys 63 which latter pulleysdefine partof the transport path. Belt 50a isdriven by the pulley 58a which is directly driven by electric motor 67. Belt 50b passes with belt 50a over pulleys 63 between pulleys 57b and 58b, and has return reaches held by fixed pulley 70, a small pulley 72 di-,

rectly driven by motor 74, and tensioning pulley 76 held by spring biased lever 78.

The feeder/stacker also comprises a stacking roller 52; a movable stop blade 54; two small high friction slow moving feed belts 56 disposed above and below belt 50a and passing over outer portions of pulleys 60 and 61; and a doubles rejection gate 59.

The stacking roller 52 is carried by a mounting 80 slideably carried by the carriage 24, and movable outwardly of the space between pulleys 60 and 61 by a cam 82 acting against the force of spring 84. The roller 52 has two highly polished wheel portions 52a which project beyond the plane of belt 50a when the mounting is moved outwards by the cam 82, to an operative position, and this roller also has a central pulley portion I of smaller diameter than wheel portions 52a driven by belt 50a when the roller is in the operative position, so that wheel portions 52a are caused to rotate. Cam 82 is carried by shaft 86 which is rotatable by solenoid 88 acting on a crank at the end of shaft 86. The other end of shaft 86 carries the stop blade 54 which is of triangular shape as shown in FIG. 4. The rotation of shaft 86 by the solenoid moves the stop blade 54 from the operative position of FIG. 4, in which the feeder/stacker is in the stacking mode and in which blade 54 is positioned adjacent the inner edge of the shelf and extends across the path of letters being moved radially inwardly of the shelf by belt 50a, to an inoperative position 45 displaced from the operative position in which it allows passage of letters from in front of pulleys 60, 61 to the inlet of the pinch belts 50a, 50b defined by pulleys 57a, 57b. Rotation of the shaft 86 in the reverse direction is caused by a spring (not shown).

The two feed belts 56 are driven by a small motor 90 via a speed reduction belt 92 and pulleys 93 shown in FIG. 4.

The doubles rejection gate 59 is pivotally carried by a mounting 94 which extends over the belts 50a, 50b, and includes a spring 96 urging a high friction edge of the gate close to belt 50a where this passes over pulley 57a.

Operation of the buffer/stacker is commenced with the shelf empty, with the carriage 24 in its uppermost position, and with the feeder/stacker 23 in the stacker mode of FIG. 3. Also, the drive motor 34 connected to rolls 32 is arranged to rotate these in such direction that the pinch rolls will carry letters L from the delivery point A to the feeder/stacker. The handle 110 is rotated to move carriage 100 so that the delivery end part 38 of the pinch belts is adjusted to suit the height of a machine delivering letters, and placed adjacent the output of the machine, and operation is commenced. Letters leaving the machine then enter the 7 pinch belts 30 ina vertical position, that is on edge with the address surface of the letter in a vertical plane.

Once in the pinch belts 36, the letters are rotated to a horizontal position, before passing into the intermediate part 37 of the pinch belts, the letters returning to the vertical position in the movable end part 39 of the pinch belts before leaving these belts between the rolls 33. The letters then pass into contact with transport belt 50a of the buffer stacker. Belt 50a moves the letters inwardly over the outer edge of shelf 20 and the first letter of a batch is wedged between abutment 20a and the stacking roller 52. Subsequent letters are similarly moved by belt 50a and wedged between the previously stacked letters and the stacking roller 52, being also moved up against the stop blade 54 adjacent the inner edge of the shelf. The stacking roller 52 driven by belt 50a lifts the letters off the belt 50a and the two wheel portions of this roller allow the letter to rest against the stop blade without damaging the letter surface. The stacking operation continuously pushes away the letters as they form the stacks, causing the shelf to rotate at suitable speed. The letters are moved directly from the conveying means onto relatively fixed positions on the shelf, there being no substantial movement of the letters around the shelf such as might cause difficulty in maintaining the stability of the stack. As the shelf rotates, the feeder/stacker and the associated part 39 of the conveyor means gradually decend to maintain a constant relationship with the surface of the shelf.

Once the shelf has been filled, it may be set aside to provide storage, or may be moved immediately to the next processing station to provide a source of letters for that operation. If necessary, the height of the delivery end part 38 of thepinch belts is adjusted by the manual means described, and the feeder/stacker is switched to the feeder mode of operation (which may be controlled remotely) this switching involving reversal of the direction of movement of the pinch belts 30, and operation of solenoid 88 which rotates the shaft 86 and the stop blade 54 through 45 and permits the letters to pass from belts 56 into pinch belts 50 between pulleys 57a, b. The shaft rotation also changes the position of cam 82 and the stacking roller 52 and belt 50a carried by the central pulley portion of roller 52 withdraws behind the two small high friction feed belts 56. These two feed belts 56 keep the letter in the stacked position and away from the transport belt 50a unless the feed motor is activated, then the slow moving belts advance the letters one by one towards the shelf axis until they enter the pinch belts 50 which grip the leading letter edge and accelerate the letter away from the stack thereby exposing the following letter to the slow moving feed belts. The high friction surface tip of the doubles rejector gate 59 allows only single letters to advance into the pinch belts. During this feeding operation, gentle rotational force is constantly applied by motor 22 to shaft 18 to keep the stacked letters pressed lightly against the feed belts 56. The friction between the doubles rejection gate and a letter is lower than the friction between the transport belt and a letter but [larger than the friction between two letters. The belts 50 carry the letters around to the discharge point between pulleys 58a and 58b, where they pass into the main pinch belts 30. During the feed operation the main pinch belts 30 are driven by the motor 34 in the reverse direction and accept the letters from the pinch belts 50 and carry them to the discharge point A.

A proposed buffer stacker in accordance with the invention would be about 3% feet high, and about 40 inches by 46 inches in cross-sectional area, and would have a helical shelf 20 with a length of about 35 feet, and capable of accommodating about 10,000 letters. The apparatus would be capable of stacking and destacking letters at approximately 10 letters per second.

I claim:

1. Apparatus for storing articles, comprising a storage unit in the form of a helical shelf with a vertical axis and which is mounted for rotation around said axis, conveying means providing for movement of said articles seriatim along a path between the shelf and a stationary delivery point outside the shelf, which path re-- mains substantially fixed in lateral position as the shelf rotates and which leads directly to different positions along the shelf dependent on the rotational position of the shelf, and means for providing relative vertical movement between the storage unit and a part of the conveyor means adjacent the shelf so as to maintain a constant relationship between said part of the conveyor means and the surface of the shelf as the shelf rotates.

2. Apparatus according to claim 1, wherein said storage unit is mounted for rotation without vertical movement, and wherein said part of the conveyor means adjacent the shelf is vertically movable by an amount equivalent to the overall axial height of the shelf.

3. Apparatus according to claim 1, wherein said conveying means includes pinch belts.

4. Apparatus for storing thin flat flexible articles, comprising a storage unit in the form of a helicalshelf with a vertical axis and which is mounted for rotation around said axis, pinch belt means for conveying said articles seriatim between the storage unit and a stationary delivery point outside the unit along a path which remains substantially fixed in lateral position as the shelf rotates and which leads directly to different positions along the shelf dependent on the rotational position of the shelf, said pinch belt means including a movable end part adjacent the shelf arranged to hold said articles vertical while moving the articles laterally to allow transfer of said articles between the pinch belt means and the shelf,'means providing vertical movement of said end part of the pinch belt means so as to maintain a constant relationship thereof to an adjacent portion of the shelf as the shelf rotates, said pinch belt means also including an intermediate part twisted through 90 relative to said movable end part, said intermediate part providing an inclined path of varying length between a delivery end part of the pinch belt means, which delivery end part is stationary in position, and the said movable end part.

5. Apparatus according to claim 4, wherein the junction between the intermediate part of the pinch belt means and the delivery end part thereof is defined by first horizontal pulley means, and wherein the junction between the said intermediate part and the said movable end part is defined by second horizontal pulley means, said second horizontal pulley means being movable vertically without lateral movement with the said the operative reaches taut in spite of movements of said second pulley means.

6. Apparatus according to claim 4, wherein said pinch belt means comprises a main set of pinch belts, which main set includes said intermediate part and a portion of the movable end part of the pinch belt means, and a further set of pinch belts forming another portion of the movable end part of the pinch belt means, said further set of pinch belts being part of a feeder/stacker operable selectively to feed articles from a stack of said articles on the shelf in side-by-side relationship and in vertical radial planes, into the main set ofpinch belts, or to transfer said articles from the main set of pinch belts onto the shelf to form a similar stack of said articles.

7. Apparatus for storing thin flat flexible articles, comprising:

a support, bearing means carried by the support and having a vertical axis,

a helical shelf co-axially mounted on said bearing means for rotation about the axis thereof,

carriage means movable vertically on-said support, means being provided for simultaneously rotating said shelf and moving said carriage means in such manner that the carriage means maintains a vertical constant relationship with the surface of the shelf,

pulley means carrying a main set of pinch belts, in-

cluding a first set of horizontal pulley means mounted on the support in stationary position, a second set of horizontal pulley means mounted on said carriage means, said first and second sets of pulley means defining the ends of an inclined path of varying length for operative reaches of the pinch belts carried thereby, and further pulleys spaced from the operative reaches of the said pinch belts for holding return reaches of said pinch belts,

and a feeder/stacker also mounted on said carriage means and including means for moving said articles between said main pinch belts and stacked positions on the shelf, in which stacked positions the articles lie in substantially vertical planes extending radially of the shelf.

8. Apparatus according to claim 7, wherein said pulley means for said main pinch belts also include vertical pulley means mounted on said carriage means and spaced horizontally from said second set of horizontal pulley means, whereby said pinch belts are twisted through on passing from said .second set of horizontal pulley means to said vertical pulley means, and wherein said feeder stacker includes a further set of pinch belts carried by further vertical pulley means and capable of receiving said articles from the main pinch belts passing around said vertical pulley means.

9. Apparatus according to claim 6, wherein said further set of pinch belts has an entry point adjacent one edge of the shelf and a discharge point adjacent an end of the main set of pinch belts, one of the belts of said further set of pinch belts also having a reach extending from said end of the main set of pinch belts to the shelf and passing over the side of the shelf opposite to said one edge.

10. Apparatus according to claim 6 wherein the feeder stacker comprises friction belt means, movable independently of said further set of pinch belts and po- 9 sitioned over said shelf so as to deliver articles from the shelf to said further set of pinch belts.

11. Apparatus according to claim 6, whereinsaid feeder/stacker includes movable stop means. against which said articles are stackedby the feeder/stacker when operating in a stacking mode, saidstop means being movable to allow feedingof said articles from the side of the ther set of pinch belts has an entry point adjacent one edge of the shelf and a discharge point adjacent an end of the main set of pinch belts, one of the belts of said further set of pinch belts also having a reach extending from said end of the main set of pinch belts to the shelf andpassing over the side of the shelf opposite to said one edge.

14. Apparatus according to claim 8, wherein the feeder stacker comprises friction belt means, movable independentlyof said further set of pinch belts and positioned over said shelf so as to deliver articles from the shelf to said further set of pinch belts.

15. Apparatus according to claim 7, wherein said feeder/stacker includes movable stop means against which said articles are stacked by the feeder/stacker when operating in a stacking mode, said stop means being movable to allow feeding of said articles from the side of the shelf opposite to that over which the articles pass when being stacked.

16. Apparatus according to claim 7, wherein said feeder/stacker is arranged to stack said articles on the shelf by movement radially inward relatively to the shelf.

17. Apparatus according to claim 7, wherein said carriage means are movable vertically by a motor controlled by sensing means carried by the carriage means and which senses the height relative to the carriage means of a portion of the shelf adjacent the carriage means.

18. Apparatus according to claim 7, wherein said first set of horizontal pulley means is mounted on further carriage means, said further carriage means being normally stationary during operation of the apparatus but being adjustable in height.

19. Apparatus according to claim 7, wherein said frame is provided with wheels to allow the apparatus to be moved, with articles stacked therein, from one location to another.

20. A process for temporarily storing flat thin articles such as letters, comprising the steps of:

moving said articles seriatim while disposed vertically into a pinch belt arrangement at stationary point, rotating said articles by said belt arrangement to dispose the articles in a horizontal plane,

moving said articles by said belt arrangement along an inclined plane to a level different from said stationary point, said inclined plane being fixed in lateral position, rotating said articles into the vertical plane and simultaneously moving said articles in a horizontal direction towards stacking means,

stacking said articles along a helical shelf, said shelf being continuously rotated during stacking so that the lateral position of the stacking operation remains fixed, while continuously raising or lowering the stacking position in accordance with the level of that part of the shelf receiving the articles.

21. A process according to claim 20, wherein said articles are stacked with one end against a stop adjacent one edge of the shelf, which stop remains in fixed posi tion relative to the stacking position during the stacking operation, said process including a subsequent step of displacing the stop from said fixed position and feeding articles from the stack on the shelf with the stop displaced to allow the articles to be fed from the shelf over 

1. Apparatus for storing articles, comprising a storage unit in the form of a helical shelf with a vertical axis and which is mounted for rotation around said axis, conveying means providing for movement of said articles seriatim along a path between the shelf and a stationary delivery point outside the shelf, which path remains substantially fixed in lateral poSition as the shelf rotates and which leads directly to different positions along the shelf dependent on the rotational position of the shelf, and means for providing relative vertical movement between the storage unit and a part of the conveyor means adjacent the shelf so as to maintain a constant relationship between said part of the conveyor means and the surface of the shelf as the shelf rotates.
 2. Apparatus according to claim 1, wherein said storage unit is mounted for rotation without vertical movement, and wherein said part of the conveyor means adjacent the shelf is vertically movable by an amount equivalent to the overall axial height of the shelf.
 3. Apparatus according to claim 1, wherein said conveying means includes pinch belts.
 4. Apparatus for storing thin flat flexible articles, comprising a storage unit in the form of a helical shelf with a vertical axis and which is mounted for rotation around said axis, pinch belt means for conveying said articles seriatim between the storage unit and a stationary delivery point outside the unit along a path which remains substantially fixed in lateral position as the shelf rotates and which leads directly to different positions along the shelf dependent on the rotational position of the shelf, said pinch belt means including a movable end part adjacent the shelf arranged to hold said articles vertical while moving the articles laterally to allow transfer of said articles between the pinch belt means and the shelf, means providing vertical movement of said end part of the pinch belt means so as to maintain a constant relationship thereof to an adjacent portion of the shelf as the shelf rotates, said pinch belt means also including an intermediate part twisted through 90* relative to said movable end part, said intermediate part providing an inclined path of varying length between a delivery end part of the pinch belt means, which delivery end part is stationary in position, and the said movable end part.
 5. Apparatus according to claim 4, wherein the junction between the intermediate part of the pinch belt means and the delivery end part thereof is defined by first horizontal pulley means, and wherein the junction between the said intermediate part and the said movable end part is defined by second horizontal pulley means, said second horizontal pulley means being movable vertically without lateral movement with the said movable end part of the pinch belt means, and wherein further pulley means are provided holding return reaches of said pinch belt means spaced away from the operative reaches thereof, said further pulley means being biased away from said operative reaches to hold the operative reaches taut in spite of movements of said second pulley means.
 6. Apparatus according to claim 4, wherein said pinch belt means comprises a main set of pinch belts, which main set includes said intermediate part and a portion of the movable end part of the pinch belt means, and a further set of pinch belts forming another portion of the movable end part of the pinch belt means, said further set of pinch belts being part of a feeder/stacker operable selectively to feed articles from a stack of said articles on the shelf in side-by-side relationship and in vertical radial planes, into the main set of pinch belts, or to transfer said articles from the main set of pinch belts onto the shelf to form a similar stack of said articles.
 7. Apparatus for storing thin flat flexible articles, comprising: a support, bearing means carried by the support and having a vertical axis, a helical shelf co-axially mounted on said bearing means for rotation about the axis thereof, carriage means movable vertically on said support, means being provided for simultaneously rotating said shelf and moving said carriage means in such manner that the carriage means maintains a vertical constant relationship with the surface of the shelf, pulley means carrying a main set of pinch belts, including a first set of horIzontal pulley means mounted on the support in stationary position, a second set of horizontal pulley means mounted on said carriage means, said first and second sets of pulley means defining the ends of an inclined path of varying length for operative reaches of the pinch belts carried thereby, and further pulleys spaced from the operative reaches of the said pinch belts for holding return reaches of said pinch belts, and a feeder/stacker also mounted on said carriage means and including means for moving said articles between said main pinch belts and stacked positions on the shelf, in which stacked positions the articles lie in substantially vertical planes extending radially of the shelf.
 8. Apparatus according to claim 7, wherein said pulley means for said main pinch belts also include vertical pulley means mounted on said carriage means and spaced horizontally from said second set of horizontal pulley means, whereby said pinch belts are twisted through 90* on passing from said second set of horizontal pulley means to said vertical pulley means, and wherein said feeder stacker includes a further set of pinch belts carried by further vertical pulley means and capable of receiving said articles from the main pinch belts passing around said vertical pulley means.
 9. Apparatus according to claim 6, wherein said further set of pinch belts has an entry point adjacent one edge of the shelf and a discharge point adjacent an end of the main set of pinch belts, one of the belts of said further set of pinch belts also having a reach extending from said end of the main set of pinch belts to the shelf and passing over the side of the shelf opposite to said one edge.
 10. Apparatus according to claim 6 wherein the feeder stacker comprises friction belt means, movable independently of said further set of pinch belts and positioned over said shelf so as to deliver articles from the shelf to said further set of pinch belts.
 11. Apparatus according to claim 6, wherein said feeder/stacker includes movable stop means against which said articles are stacked by the feeder/stacker when operating in a stacking mode, said stop means being movable to allow feeding of said articles from the side of the shelf opposite to that over which the articles pass when being stacked.
 12. Apparatus according to claim 6, wherein said feeder/stacker is arranged to stack said articles on the shelf by movement radially inward relatively to the shelf.
 13. Apparatus according to claim 8, wherein said further set of pinch belts has an entry point adjacent one edge of the shelf and a discharge point adjacent an end of the main set of pinch belts, one of the belts of said further set of pinch belts also having a reach extending from said end of the main set of pinch belts to the shelf and passing over the side of the shelf opposite to said one edge.
 14. Apparatus according to claim 8, wherein the feeder stacker comprises friction belt means, movable independently of said further set of pinch belts and positioned over said shelf so as to deliver articles from the shelf to said further set of pinch belts.
 15. Apparatus according to claim 7, wherein said feeder/stacker includes movable stop means against which said articles are stacked by the feeder/stacker when operating in a stacking mode, said stop means being movable to allow feeding of said articles from the side of the shelf opposite to that over which the articles pass when being stacked.
 16. Apparatus according to claim 7, wherein said feeder/stacker is arranged to stack said articles on the shelf by movement radially inward relatively to the shelf.
 17. Apparatus according to claim 7, wherein said carriage means are movable vertically by a motor controlled by sensing means carried by the carriage means and which senses the height relative to the carriage means of a portion of the shelf adjacent the carriage means.
 18. Apparatus according to claim 7, wherein said first set of horizontal pulley means is mounted on further caRriage means, said further carriage means being normally stationary during operation of the apparatus but being adjustable in height.
 19. Apparatus according to claim 7, wherein said frame is provided with wheels to allow the apparatus to be moved, with articles stacked therein, from one location to another.
 20. A process for temporarily storing flat thin articles such as letters, comprising the steps of: moving said articles seriatim while disposed vertically into a pinch belt arrangement at stationary point, rotating said articles by said belt arrangement to dispose the articles in a horizontal plane, moving said articles by said belt arrangement along an inclined plane to a level different from said stationary point, said inclined plane being fixed in lateral position, rotating said articles into the vertical plane and simultaneously moving said articles in a horizontal direction towards stacking means, stacking said articles along a helical shelf, said shelf being continuously rotated during stacking so that the lateral position of the stacking operation remains fixed, while continuously raising or lowering the stacking position in accordance with the level of that part of the shelf receiving the articles.
 21. A process according to claim 20, wherein said articles are stacked with one end against a stop adjacent one edge of the shelf, which stop remains in fixed position relative to the stacking position during the stacking operation, said process including a subsequent step of displacing the stop from said fixed position and feeding articles from the stack on the shelf with the stop displaced to allow the articles to be fed from the shelf over the said one edge. 